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Posted: 6/4/2006 1:19:02 PM EDT
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The problem I have is the current set up is a large hole upper and lower. I have several other small hole uppers. I am also looking at getting a 9mm upper. Do they make a sleeve so I can use a small pin upper on my large pin lower?? Or do I need to find only large pin uppers? I even bought an extra upper thinking I could swap it out with ease on the M16 lower.......any help would be appreciated! |
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Its actually very common to have this happen with Colts. You need a conversion pin if you are going from a large hole lower to a small hole upper. Brownells sells a bushing for a few bucks if you are using a large hole upper and a small hole lower. There are tons of pins and bushings around. You dont need to buy the entire kits. You can do well with just the bushing or pin depending on the situation. |
If you want to permanently eliminate the need for an adapter, send your lower to Mike Klos of American Manufaturing. He weld up the large pivot hole, and redrill the hole to small pivot specs in a genuine Colt drilling jig. Then you can use small-pivot uppers to your heart's desire. 
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Bushmaster has the offset pins for $6.50 www.bushmaster.com/shopping/lowers/nes-06.asp |
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Just a personal observation about the offset pins. I have a Colt SP1 conversion and shoot 4 different calibers. The pin Bushmaster sells works but I prefer the pin with a large slotted head on one side. It looks similar to the Colt pin you are replacing. These seem to stay tighter longer than the other style for me. The caliber that really shakes it loose in a hurry is the 7.62x39, I need to snug it after 2 mags. 9mm is normally not a problem as I run an Oly small hole upper which remains tight. I have a large hole upper from Daniel Defense and they are nice if you don't mind spending the money. Another option if you have an abundance of small hole uppers in the safe is to have them opened up to large hole specs. M60joe will do this for $40 + $6 shipping - this mod along with using a KNS large push pin looks good to me. Remember alot of big hole Colt uppers off semi guns (SP1's) don't have the sear relief cut and will not work on a FA gun. I just can't convince myself to send the lower off for a weld job. I'll have to deal with the hassle of 2 screw drivers in the range bag for a while longer until I finally grow tried of it or modify all the uppers to .315" pin size. HTH |
The large hole would have to be welded up then redrilled to small hole specs, as the centers of the large and small pivot holes are not in the same place. It's not as simple as just drilling out a small pivot. I'd also be concerned about there being enough"meat" left around the hole in the pivot lug after such a conversion.  
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Colt large hole uppers are out there, a bit pricy though for flattops. They have to be machined for the sear relief, cost me $55 to have one done locally. There are large hole 9mm A1 uppers floating around: I've heard rumors of a Colt 9mm flattop but have never seen one. Daniel Defense also makes/made a large hole flattop upper w/sear relief. Pricy, but not as much as Colt. 
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Man you Texicans must love to spend money. $55 to mod a Colt upper for auto sear clearance? How about 10 minutes w/a good quality needle file to cut a notch on ech side of the upper?And pay to have holes welded up? Man, three of the DPMS sleeves, a small hole spring loaded push pin, a tube of JB Weld to secure the sleeves, a good head on your shaoulders, and you can small hole a big hole Colt, AND if you cut the sleeves the right length, you can leave a surface in the right side lug that will catch and retain the push pin----and you won't have to either live w/the remnents of welding or pay a bunch more to have the lower reanodised. Oh, I forgot there for awhile. Most of you guys have more bucks that should be allowed anyway, and bought your class three pieces for thousands of dollars. I'm just a poor guy who bought an SP1 carbine back in the '70s, paid $250 (fifty for the machining and $200 to Uncle Sam) in 1979 for the conversion. Of course I'm also the guy who bought an M1 Thompson for $59.95 in 1965, paid Uncle the $200, and thought I was doing well when I sold it for $1000 in 1979  Well in the event that there are some other poor working folks out there, that's how you can small hole an SP1, 2 or early Sporter without taking your kids food off the table. 
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Ya mean like this? www.uzitalk.com/forums/showthread.php?t=19151 M60Joe sleeves them, though he pins them in place. A quick coat of moly and your RR is done. I highly recommend his work: 
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I have five uppers for mine. 20" original, 7" Kitty-Kat, 10.25", 16" blaster (for dumping Beta mags) and a 16" dedicated .22 upper. I get a large hole upper, about 80.00, have a machinist friend mill the relief for 20.00 and put it together. Bushmaster sells a large hole push pin with a ball detent on one end. Push it through, swap the upper, back running. No double screws, no welding. Works great. |
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